The "vanish'd hand"

OK, there aren't any zombies in this poem, but the speaker's dead friend is still an important part of "Break, break, break" – after all, he's the motivation for writing. The speaker never comes out and says, "my friend died," he just keeps talking about how much he'd like to shake that "vanish'd hand" one more time, or hear "the voice that is still." The dead friend is never named, but he's an important presence in the poem, anyway. He's not even described. He's just represented by a series of absences: the absent hand, the absent voice, and finally the absent time (the "day that is dead") that the poet knows will never come back.

• Line 11: The speaker uses synecdoche when he imagines that his friend's "vanish'd hand" is a stand-in for the whole person.
• Line 12: More synecdoche. The friend's "voice," like his "vanish'd hand," is meant to stand in for the whole person. Why don't we get any descriptions of the friend? Why these references to the missing parts of him?